Method of producing silicone emulsion

ABSTRACT

A method of obtaining an aqueous silicone emulsion which dries to an elastomer comprises mixing (1) hydroxyl endblocked polydiorganosiloxane free of aliphatic unsaturation, (2) silicon hydride crosslinker, (3) platinum compound catalyst compatiable with the polydiorganosiloxane, (4) catalyst inhibitor, (5) anionic or nonionic surfactant, and (6) water and polymerizing the polydiorganosiloxane. These ingredients can be combined in emulsion form following three differing versions of a method of combining the ingredients and polymerizing the polydiorganosiloxane. In each case, the emulsion, which may also contain filler, is useful as a coating or sealant.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to method of making silicone emulsions whichyield an elastomer upon removal of the water at ambient conditions.

2. Background Information

Silicone paper release coatings are taught in U.S. Pat. No. 4,190,688,issued Feb. 26, 1980. The emulsion comprises a vinyl-containingpolydiorganosiloxane having hydroxyl endblocking, a hydridecross-linking agent, water, and an emulsifying agent. The compositioncan be cured either with a tin salt of a carboxylic acid or it can becured with a platinum complex catalyst.

A latex of crosslinked silicone is prepared in U.S. Pat. No. 4,248,751,issued Feb. 3, 1981, by emulsifying a vinyl endblockedpolydiorganosiloxane and an organosilicon compound having silicon-bondedhydrogen atoms with water and a surfactant, adding platinum catalyst,and then heating the emulsion. Colloidal silica can be added to theemulsion to provide a tougher product.

SUMMARY OF THE INVENTION

Elastomeric films and coatings can be produced by drying emulsions whichare the product obtained by reacting hydroxyl endblockedpolydiorganosiloxane free of unsaturation. silicon hydride crosslinker,and a platinum compound compatible with the polydiorganosiloxane, in thepresence of surfactant, and water.

DESCRIPTION OF THE INVENTION

This invention relates to a method of producing an aqueous siliconeemulsion which dries to an elastomer comprising (A) homogenizing amixture of (1) 100 parts by weight of hydroxyl endblockedpolydiorganosiloxane free of aliphatic unsaturation, (2) from 0.1 to 10parts by weight of silicon hydride crosslinker, (3) sufficient platinumcompound catalyst. compatible with the polydiorganosiloxane, to givefrom 1 to 200 parts by weight of platinum per million parts ofpolydiorganosiloxane (1), (4) catalyst inhibitor, (5) anionic ornonionic surfactant, and (6) sufficient water to yield apolydiorganosiloxane content in the mixture of from 40 to 70 percent byweight, (B) emulsion polymerizing the mixture of (A) by addition ofanionic polymerization catalyst to give a polymer, then (C) arrestingpolymerization by raising the pH to 6 to 7.5, whereby an aqueoussilicone emulsion is obtained which gives an elastomer upon removal ofthe water at room temperature.

This invention also relates to a method of producing an aqueous siliconeemulsion which dries to an elastomer comprising (A) homogenizing amixture of (1) 100 parts by weight of hydroxyl endblockedpolydiorganosiloxane free of aliphatic unsaturation, (2) from 0.1 to 10parts by weight of silicon hydride crosslinker, (5) anionic or nonionicsurfactant. and (6) sufficient water to yield a polydiorganosiloxanecontent in the mixture of from 40 to 70 percent by weight then (B)emulsion polymerizing the mixture of (A) by addition of anionicpolymerization catalyst to yield a polymer, then (C) arrestingpolymerization by raising the pH to 6 to 7.5. to obtain emulsion A, then(D) homogenizing a mixture of (1) from 0 to 100 parts by weight ofhydroxyl endblocked polydiorganosiloxane, and (3) platinum compoundcatalyst, compatible with the polydiorganosiloxane, (5) anionic ornonionic surfactant, and (6) water, then, when (1) is greater than 0,(E) emulsion polymerizing the mixture of (D) by addition of anionicpolymerization catalyst, then (F) arresting polymerization by raisingthe pH to 6 to 7.5, to obtain emulsion B, then (G) mixing emulsion A andsufficient emulsion B to obtain from 1 to 200 parts by weight ofplatinum per million parts of polydiorganosiloxane (1), whereby anaqueous silicone emulsion is obtained which gives an elastomer uponremoval of the water at room temperature.

This invention also relates to a method of producing an aqueous siliconeemulsion which dries to an elastomer comprising (A) homogenizing amixture of (1) 100 parts by weight of hydroxyl endblockedpolydiorganosiloxane free of aliphatic unsaturation, and (3) sufficientplatinum compound catalyst, compatible with the polydiorganosiloxane, togive from 1 to 200 parts by weight of platinum per million parts ofpolydiorganosiloxane (1), (5) anionic or nonionic surfactant, and (6)sufficient water to give a polydiorganosiloxane content in the mixtureof from 40 to 70 percent by weight, then (B) emulsion polymerizing themixture of (A) by addition of anionic polymerization catalyst, then (C)arresting polymerization by raising the pH to 6 to 7.5, to obtainemulsion A, then (D) homogenizing a mixture of (2) silicon hydridecrosslinker, (5) anionic or nonionic surfactant, and (6) water, toobtain emulsion B, then (E) mixing emulsion A and emulsion B insufficient quantity to obtain from 0.1 to 10 parts by weight of siliconhydride crosslinker in Emulsion B per 100 parts by weight of hydroxylendblocked polydiorganosiloxane in Emulsion A, whereby an aqueoussilicone emulsion is obtained which gives an elastomer upon removal ofthe water at room temperature.

The hydroxyl endblocked polydiorganosiloxane (1) can be chosen from anyof such well known and available materials, however, the material chosenshould have a viscosity such that it can be easily emulsified, a fluidmaterial is preferred such as a material having a viscosity of less than250 cps at 25° C. The organic groups can be any of those commonly usedin polydiorganosiloxanes (excluding groups containing aliphaticunsaturation) such as monovalent substituted and unsubstituted alkylradicals: with preferred radicals being methyl, ethyl, propyl, and3,3,3-trifluoropropyl, and monovalent aryl radicals, such as phenyl. Apreferred polymer is a hydroxyl endblocked polydimethylsiloxane having adegree of polymerization of about 35 and a viscosity of about 80 cps at25° C (0.08 Pa.s).

The silicon hydride crosslinker (2) can be chosen from hydrolyzablesilicon hydride, polyorganohydrogensiloxane, alkylhydrogencyclosiloxane,and liquid copolymers comprising SiO₂ and bearing silicon-bondedhydrogen radicals such as are taught in U.S. Pat. No. 4,310,678, issuedJan. 12, 1982, which patent is hereby incorporated by reference to showsuch silicon-bonded hydrogen radical containing materials and how theyare manufactured. The hydrolyzable silicon hydride should have at leastone, but no more than three hydrogen atoms bonded to silicon permolecule. It should have one or two hydrolyzable atoms or radicals, suchas alkoxy, bonded to silicon per molecule, such as methyldiethoxysilane.A preferred crosslinker is trimethylsilyl endblockedpolymethylhydrogensiloxane. Another preferred crosslinker ismethylhydrogencyclosiloxane.

The platinum compound catalyst (3), compatible with thepolydiorganosiloxane, is selected from any of those well known to theart, such as those described in U.S. Pat. No. 3,923,705, issued Dec. 2,1975, said patent being hereby incorporated by reference to showplatinum catalysts. A preferred platinum compound catalyst is acomposition consisting essentially of the reaction product ofchloroplatinic acid and an organosilicon compound containing terminalaliphatic unsaturation, such as are described in U.S. Pat. No.3,419,593, issued Dec. 31, 1968, said patent being incorporated byreference to describe suitable platinum compounds and their method ofmanufacture, where chloroplatinic acid hexahydrate is mixed withsymmetrical divinyltetramethyldisiloxane to provide the complex. It isthought that homogeneous triphenylphosphine-platinum complexes such asare commonly used in organic synthesis as homogeneous catalysts will befunctional in this invention. A preferred catalyst is a chloroplatinicacid complex of divinyltetramethyldisiloxane.

A catalyst inhibitor (4) is used to slow down the reaction between thehydroxyl endblocked polydiorganosiloxane free of aliphatic unsaturationand the silicon hydride crosslinker in the presence of the platinumcompound catalyst during the mixing step before homogenization. Thecatalyst inhibitor can be any of the well known inhibitors forpreventing platinum catalyzed reaction between unsaturated groups suchas vinyl on silicon and hydrogen on silicon. Useful inhibitors aredescribed in U.S. Pat. No. 3,445,420, issued May 20, 1969, whichdescribes acetylenic inhibitors; U.S. Pat. No. 3,989,667, issued Nov. 2,1976 which describes olefinic siloxanes; and U.S. Pat. No. 4,585,848,issued Apr. 29, 1986, which describes maleate inhibitors. Preferredinhibitors include diethylmaleate and methyl butynol.

The surfactant (5) can be an anionic surfactant, a nonionic surfactant,or a mixture of each. Surfactants useful in emulsifying silicone fluidsare well known and include alkali metal sulforicinates, sulfonatedglyceryl esters of fatty acids, salts of sulfonated monovalent alcoholesters, amides of amino sulfonic acid such as the sodium salt of oleylmethyl tauride. sulfonated aromatic hydrocarbon alkali salts such assodium alpha-naphthalene monosulfonate, condensation products ofnaphthalene sulfonic acids with formaldehyde, and sulfates such asammonium lauryl sulfate, triethanol amine lauryl sulfate and sodiumlauryl ether sulfate. Preferred anionic surfactants are salt of thesurface active sulfonic acids as shown in U.S. Pat. No. 3,294,725,issued Dec. 27, 1966, hereby incorporated by reference to show suitableanionic surfactants, and sulfates. A preferred surfactant is sodiumlauryl sulfate.

Nonionic surfactants can be illustrated by saponins, condensationproducts of fatty acids with ethylene oxide such as dodecyl ether oftetraethylene oxide, condensation products of ethylene oxide andsorbitan trioleate, condensation products of phenolic compounds havingside chains with ethylene oxide such as condensation products ofethylene oxide with isododecylphenol, and imine derivatives such aspolymerized ethylene imine.

Sufficient water (6), preferably deionized, is added to the mixture togive a polymer content of the emulsion of from 40 to 70 percent byweight. The preferred polymer content of the emulsion is from 60 to 65percent by weight.

The hydroxyl endblocked polydiorganosiloxane (1) is emulsion polymerizedthrough the use of an anionic polymerization catalyst. The emulsion isemulsion polymerized by the addition of an anionic polymerizationcatalyst such as strong mineral acids as taught in U.S. Pat. No.2,891,920, issued June 23, 1959 or surface active sulfonic acid catalystas taught in U.S. Pat. No. 3,294,725, issued Dec. 27, 1966, both patentsbeing incorporated by reference to show suitable anionic polymerizationcatalysts, their preparation and use. The catalyst lowers the pH to 2 orless. Preferred catalysts are hydrochloric acid, sulfuric acid, anddodecylbenzene sulfonic acid.

The method of reacting the ingredients (1) through (6) is selected fromthe variations described below. Each of the variations combines the sameingredients, but in a different manner; so that the aqueous siliconeemulsion that is produced dries to an elastomer, but the elastomermolecular configuration may depend upon the variation by which it wasproduced. For convenience, each variation will be referred to by number.

Method one relates to a method of producing an aqueous silicone emulsionwhich dries to an elastomer comprising (A) homogenizing a mixture of (1)100 parts by weight of hydroxyl endblocked polydiorganosiloxane free ofaliphatic unsaturation, (2) from 0.1 to 10 parts by weight of siliconhydride crosslinker, (3) sufficient platinum compound catalyst,compatible with the polydiorganosiloxane, to give from 1 to 200 parts byweight of platinum per million parts of polydiorganosiloxane (1), (4)catalyst inhibitor, (5) anionic or nonionic surfactant, and (6)sufficient water to yield a polydiorganosiloxane content in the mixtureof from 40 to 70 percent by weight, (B) emulsion polymerizing themixture of (A) by addition of anionic polymerization catalyst to give apolymer, then, (C) arresting polymerization by raising the pH to 6 to7.5. whereby an aqueous silicone emulsion is obtained which gives anelastomer upon removal of the water at room temperature.

The first step of this method consists of mixing the ingredientstogether. The order of mixing is not critical, except that a catalystinhibitor must be added before the catalyst. In this method, thehydroxyl endblocked polydiorganosiloxane (1), silicon hydride complex(2), and the platinum compound catalyst (3) are all present in the sameemulsion micelle; therefore, a catalyst inhibitor is necessary becausethese three ingredients react spontaneously at room temperature. Each ofthe ingredients must be compatible with the mixture. After theingredients are mixed together the water and surfactant are added andthe mixture is stirred until uniform. The uniform mixture is homogenizedusing any of the known homogenizers to give the stable emulsion.

The amounts of the ingredients can be determined, based upon thepolydiorganosiloxane (1), which is 100 parts by weight. The siliconhydride crosslinker normally varies from about 0.1 to 10 parts byweight, depending upon what crosslinker is used, with a preferred amountof from 0.1 to 5 parts by weight. A preferred embodiment uses from 0.5to 2 percent by weight of methylhydrogencyclosiloxane. The preferredamount of silicon hydride crosslinker should give at least one mole ofhydrogen on silicon for each mole of hydroxyl radical on silicon in thepolydiorganosiloxane, but this is not absolutely necessary. If there isinsufficient crosslinker to react with all of the hydroxyl, theresulting elastomer may be tacky on the surface and the physicalproperties will not be as desirable as when the amount of crosslinker issufficient to give complete reaction with all of the hydroxyl radicals.When more than enough crosslinker is added, the excess crosslinker cancondense with itself, giving domains of very high crosslink density. Atsome point, these high crosslink density areas lead to poorer physicalproperties. The optimum amount of crosslinker can be determined byexperimental means with little difficulty.

The platinum compound catalyst is present in an amount to give from 1 to200 parts by weight of platinum as metal per one million parts by weightof the polydiorganosiloxane (1). The preferred amount is from 50 to 100parts per million. Excess catalyst can cause color, possible shelf lifeproblems, and excessive cost.

The catalyst inhibitor is present in an amount sufficient to give from1.5 to 10 times the stoichiometric amount needed to react with theplatinum used on a molar basis. As the amount of inhibitor is increased,the time necessary for cure can also increase. The inhibitor is presentin sufficient amount to allow the ingredients to be mixed, homogenized,and polymerized. Once the homogeneous emulsion is formed, thepolydiorganosiloxane polymer is polymerized and the desired highmolecular weight hydroxyl endblocked polymer is formed, the inhibitorlooses its effect, due to the length of time that it has been in contactwith the ingredients of the emulsion. After the inhibitor looses itseffect, the crosslinking reaction between the hydroxyl radicals on thepolymer and the hydrogen radicals on the crosslinker proceeds, yieldinga crosslinked polymer present in the emulsion particles. The timerequired for this all to occur depends upon the inhibitor used, theratio of inhibitor to platinum catalyst, and the temperature of theemulsion.

The surfactant is used in an amount sufficient to give a stableemulsion. Generally less than 2 parts by weight can be used. If too muchsurfactant is used, it can affect the physical properties of theresulting elastomer.

Sufficient water is used to give from 10 to 80 percent by weight solidsin the final emulsion. The amount of water should give apolydiorganosiloxane content in the mixture before polymerization offrom 40 to 70 percent by weight, the emulsion preferably has a polymercontent of between 40 and 65 percent by weight, with from 60 to 65percent most preferred. The solids content of the final emulsion is thatportion of the total emulsion which is not volatile. It includes thepolymer. crosslinker, surfactant, and filler, if any is present.

After the emulsion of step (A) is prepared, the polydiorganosiloxane inthe emulsion is emulsion polymerized by the addition of an anionicpolymerization catalyst such as strong mineral acids as taught in U.S.Pat. No. 2.891.920. issued June 23, 1959 or surface active sulfonic acidcatalyst as taught in U.S. Pat. No. 3,294,725, issued Dec. 27, 1966. Thecatalyst lowers the pH to 2 or less. Preferred catalysts arehydrochloric acid, sulfuric acid, and dodecylbenzene sulfonic acid. Thepolymerization will proceed satisfactorily at room temperature. Thepreferred temperature is from 25 to 90° C. The time is not critical butwill vary depending upon the speed of the reaction and the viscosity ofthe polymer that is desired. A preferred condition is 20 hours at roomtemperature.

Once the polymerization has proceeded to the desired degree, thepolymerization is stopped by raising the pH to from 6 to 7.5. The pH israised by adding a neutralizing material such as an alkaline materialsuch as alkali metal hydroxide or organic amine, preferably in the formof an aqueous solution, such as 20 percent by weight alkaline materialin water. Adding the alkaline material as an aqueous solution helpseliminate the possibility of the emulsion being broken by the additionof a concentrated material. Preferred neutralizing materials aresolutions of sodium hydroxide and solutions of diethylamine.

The aqueous silicone emulsion produced by the method of this inventiondries to an elastomer upon the removal of the water, which can be doneat room temperature by merely exposing the emulsion to the atmosphereand allowing the water to evaporate. The temperature can be raised tohasten the drying if desired. The elastomer produced by this process canbe filled with any of the well known reinforcing or non-reinforcingfillers useful with silicone elastomers as long as the filler is chosenso that it does not effect the pH of the emulsion so that it goes out ofthe required range of from 6 to 7.5. Common reinforcing fillers includefumed silica, colloidal silica dispersions, fumed titanium dioxide, andcolloidal titanium dioxide dispersions. Non-reinforcing fillers includeground quartz, calcium carbonate, non-acidic carbon black, clays,aluminum oxide, zinc oxide, mica, and various coloring pigments. Thesefillers should be finely divided and it may be advantageous to add themas aqueous dispersions. The amount of filler added is not critical, itis chosen to give the desired effect, such as increased tensilestrength, or increased hardness or increased modulus for the resultingelastomer. A preferred reinforcing filler is an aqueous, dispersed,fumed silica. A preferred non-reinforcing filler is calcium carbonate.

The emulsion produced by this method is useful as a coating and as asealant. The characteristics of the emulsion can be varied to give thedesired characteristics, such as a very flowable, liquid material, or athick, non-slumping paste, by varying the ingredients. The viscosity ofthe polydiorganosiloxane produced in the emulsion, the solids content ofthe emulsion, and the fillers used can all be varied to give the desiredproperties for the emulsion and the elastomer produced from theemulsion.

The above method one can be varied to give a method two. Method tworelates to a method of producing an aqueous silicone emulsion whichdries to an elastomer comprising (A) homogenizing a mixture of (1) 100parts by weight of hydroxyl endblocked polydiorganosiloxane free ofaliphatic unsaturation, (2) from 0.1 to 10 parts by weight of siliconhydride crosslinker, (5) anionic or nonionic surfactant, and (6)sufficient water to yield a polydiorganosiloxane content in the mixtureof from 40 to 70 percent by weight, then (B) emulsion polymerizing themixture of (A) by addition of anionic polymerization catalyst to yield apolymer, then (C) arresting polymerization by raising the pH to 6 to 7.5, to obtain emulsion A, then (D) homogenizing a mixture of (1) from 0 to100 parts by weight of hydroxyl endblocked polydiorganosiloxane free ofaliphatic unsaturation, and (3) platinum compound catalyst, compatiblewith the polydiorganosiloxane, (5) anionic or nonionic surfactant, and(6) water, then, when (1) is greater than 0, (E) emulsion polymerizingthe mixture of (D) by addition of anionic polymerization catalyst, then(F) arresting polymerization by raising the pH to 6 to 7.5, to obtainemulsion B. then (G) mixing emulsion A and sufficient emulsion B toobtain from 1 to 200 parts by weight of platinum per million parts ofpolydiorganosiloxane (1). whereby an aqueous silicone emulsion isobtained which gives an elastomer upon removal of the water at roomtemperature.

Method two is varied from method one in that the platinum compoundcatalyst (3) is removed from emulsion A and made into an emulsion Balong with part of the polydiorganosiloxane (1). Since the catalyst ispresent in a different micelle in the emulsion than that containing thesilicon hydride crosslinker, there is no need for the catalyst inhibitor(4) in the mixture when this version of the method is used. Method onegives an emulsion having a crosslinked particle in the emulsion sinceall of the required ingredients are in the same particle or micelle.Method two does not give a crosslinked particle until the emulsion isdried. During the drying process, the particles or micelles of emulsionA containing the hydroxyl endblocked polydiorganosiloxane and siliconhydride crosslinker are forced into contact with the micelles ofemulsion B containing the rest of the polydiorganosiloxane and theplatinum compound catalyst so that the reaction between thepolydiorganosiloxane and the crosslinker is catalyzed and thecrosslinking takes place. Both emulsions contain polymer so that thereis no or little migration between micelles in the emulsion. Duringdrying, the different micelles are forced together and readily coalescebecause they are very compatible. Mixing the platinum catalyst with thehydroxyl endblocked polydiorganosiloxane before polymerization andemulsifying results in a very good dispersion of the catalyst in theemulsion. When a method is attempted in which the catalyst is added toemulsion A without emulsifying, the result is a film which cures to anelastomer, but one in which there are brown spots, due to the poordispersion of the catalyst. Emulsion B can be made with varying amounts,including 0, of the polydiorganosiloxane present with the catalyst. Itis preferred that a part of the polydiorganosiloxane be present inemulsion B because it results in a more stable emulsion and a bettercompatibility of the particles of the two emulsions during drying. Whenthe amount of (1) is 0, there is no need, of course, for the emulsionpolymerizing step (E) and the arresting polymerization step (F). Theemulsion of the catalyst does, however, allow a good dispersion of thetwo emulsions so that there are no high concentrations of catalystpresent in the final emulsion, as there are when just the catalyst isadded to emulsion A.

A third version of the method of this invention combines thepolydiorganosiloxane and catalyst in emulsion A and the crosslinker inemulsion B. Method three relates to a method of producing an aqueoussilicone emulsion which dries to an elastomer comprising (A)homogenizing a mixture of (1) 100 parts by weight of hydroxyl endblockedpolydiorganosiloxane free of aliphatic unsaturation, and (3) sufficientplatinum compound catalyst, compatible with the polydiorganosiloxane, togive from 1 to 200 parts by weight of platinum per million parts ofpolydiorganosiloxane (1). (5) anionic or nonionic surfactant, and (6)sufficient water to give a polydiorganosiloxane content in the mixtureof from 40 to 70 percent by weight, then (B) emulsion polymerizing themixture of (A) by addition of anionic polymerization catalyst, then (C)arresting polymerization by raising the pH to 6 to 7.5, to obtainemulsion A, then (D) homogenizing a mixture of (2) silicon hydridecrosslinker, (5) anionic or nonionic surfactant, and (6) water, toobtain emulsion B, then (E) mixing emulsion A and emulsion B insufficient quantity to obtain from 0.1 to 10 parts by weight of siliconhydride crosslinker in Emulsion B per 100 parts by weight of hydroxylendblocked polydiorganosiloxane in emulsion A, whereby an aqueoussilicone emulsion is obtained which gives an elastomer upon removal ofthe water at room temperature.

Because emulsion B contains only the silicon hydride crosslinker and thecrosslinker is not copolymerized with the polydiorganosiloxane, thecrosslinker is free to migrate out of the emulsion micelle. For thisreason, the shelf life of the emulsion in which emulsion A and emulsionB are combined is not as long as for the other versions. In methodthree, it is preferred that the emulsion A and emulsion B be storedseparately, then combining them shortly before use. Upon drying, themicelles of emulsion A and of emulsion B are forced together, theingredients react, and an elastomeric product is the result.

The following examples are included for illustrative purposes only andshould not be construed as limiting the invention which is properly setforth in the appended claims.

EXAMPLE 1

First, 709.2 g of hydroxyl endblocked polydimethylsiloxane having aviscosity of about 0.08 Pa.s, 3.56 g of trimethylsiloxy endblockedpolymethylhydrogensiloxane having a viscosity of about 0.13 Pa.s at 25°C. and a silicon-bonded hydrogen atom content of about 1.6 percent byweight, and 3.56 g of diethylmaleate were stirred for several minutesuntil a solution resulted. Then 10.7g of a chloroplatinic acid complexof divinyltetramethyldisiloxane diluted with dimethylvinylsiloxyendblocked polydimethylsiloxane to provide 0.7 weight percent platinumwas added to this solution and it was stirred for several minutes toeffect dissolution. Next 25g of a 30 percent aqueous solution of sodiumlauryl sulfate and 341g of distilled and deionized water were added andthe mixture was stirred for 30 minutes. The mixture was homogenizedusing a single stage laboratory homogenizer at 7,500 psi to produce anoil in water emulsion having an average particle size of about 0.35micrometers. The emulsion was polymerized by adding 8g of 4Nhydrochloric acid to the emulsion and shaking it for several minutes ina closed container. The emulsion was allowed to stand at roomtemperature for 20 hrs. without agitation to complete the polymerizationprocess. Emulsion polymerization was terminated by adding enough 2percent aqueous sodium hydroxide solution to raise the pH of theemulsion to 6 to 7.5. This emulsion polymer consisted of apolydimethylsiloxane / 0.5 weight percent polymethylhydrogen copolymerhaving a weight average molecular weight of about 220,000 and containing0.5 wt percent diethylmaleate (a catalyst inhibitor) and 100 ppmplatinum. The emulsion was approximately 62 percent solids by weight.

A film was cast from this emulsion by pouring 8.0g of emulsion into a100 mm diameter plastic Petri dish and allowing it to dry under ambientconditions for 4 days. The resulting film was elastomeric.

A reinforced elastomeric film was prepared by mixing 15 g of thisemulsion with 7.2 g of aqueous, dispersed, fumed silica (Cabosperse),having a percent solids of 15.5 by weight, a pH of 7.7 and a surfacearea of 200m2/g. This mixture was shaken in a closed container forseveral minutes, centrifuged to exclude air bubbles and poured into aPetri dish. After drying for 7 days at ambient conditions, mechanicalproperties of the elastomeric film were determined. The elastomer had112 psi ultimate tensile strength and 350 percent ultimate elongation.

EXAMPLE 2

To 645.6 g of the hydroxyl endblocked polydimethylsiloxane of Example 1was added 3.24 g of the trimethylsiloxy endblockedpolymethylhydrogensiloxane of Example 1 and the mixture was stirredseveral minutes until dissolution occurred. Then 25 g of a 30 percentaqueous solution of sodium lauryl sulfate and 309.8 g of distilled anddeionized water were added and the mixture was stirred for 30 minutes.Next the mixture was homogenized using a laboratory single stagehomogenizer at 7500 psi to produce an emulsion having an averageparticle size of 0.33 micrometer and a solids content of about 62 to 65percent by weight. The emulsion was polymerized by adding 6 g of 4Nhydrochloric acid and shaking the emulsion several minutes in a closedcontainer. The emulsion was allowed to stand at room temperature for 20hrs after which polymerization was terminated by adding enough 2 percentaqueous sodium hydroxide solution to raise the pH to 6 to 7.5. Thisemulsion (emulsion A) consisted of a polydimethylsiloxane / 5 weightpercent polymethylhydrogensiloxane copolymer and was reserved for usewith a second emulsion described below.

To 648.9 g of the hydroxyl endblocked polydimethylsiloxane fluid usedabove was added 9.98g of the platinum catalyst used in Example 1 and themixture was stirred for several minutes to effect dissolution. Then 25gof a 30 percent aqueous solution of sodium lauryl sulfate and 309.8 g ofdistilled and deionized water were added and the mixture was stirred for30 minutes. The mixture was homogenized using a single stage laboratoryhomogenizer at 7500 psi to produce an emulsion having an averageparticle size of about 0.33 micrometer. The emulsion was polymerized byadding 6 g of 4N hydrochloric acid and shaking it for several minutes.The emulsion was allowed to stand for 21 hrs at room temperature, afterwhich polymerization was terminated by adding enough 2 percent aqueoussodium hydroxide solution to raise the pH of the emulsion to 6.5 to 7.5.This emulsion (emulsion B) consisted of an approximately 62 percent byweight solids polydimethylsiloxane emulsion polymer having a weightaverage molecular weight of about 250,000 and also containing 100 ppmPlatinum.

Then 100 g of the above described emulsion B (containing the Ptcatalyst) was mixed with an equal weight of the previously describedemulsion A (polydimethylsiloxane /polymethylhydrogensiloxane copolymer)and stirred for several minutes. The resulting mixture consisted of anapproximately 62 percent solids emulsion of polydimethylsiloxane - 0.25wt percent polymethylhydrogen siloxane that contained 50ppm platinumbased on polymer weight. Films were cast from this emulsion and airdried for 24 hours; they were elastomeric. A portion of this emulsionwas mixed with enough aqueous, dispersed, fumed silica (Cabosperse F) toprovide an emulsion containing 10 pph silica by weight of polymer.Cabosperse F is 12 percent by weight solids, has a pH of from 7.5 to7.8, a viscosity of less than 100 cps., and a nominal particle size of 7nanometers. A film was cast from this emulsion and it was allowed to dryunder ambient conditions. Two weeks later mechanical properties of thefilm were determined. The elastomeric film had 130 psi ultimate tensilestrength and 400 percent ultimate elongation.

EXAMPLE 3

First, an emulsion A was prepared by weighing 648.9 g of the hydroxylendblocked polydimethylsiloxane of Example 1 and 10.7 g of thechloroplatinic acid complex of divinyltetramethyldisiloxane diluted withdimethylvinylsiloxy endblocked polydimethylsiloxane of Example 1 into abeaker and stirring the mixture for several minutes to effectdissolution. Next 26.5 g of a 30% aqueous solution of sodium laurylsulfate and 309.8 g of deionized water were added and the mixture wasstirred for 30 minutes. The mixture was homogenized using a single stagelaboratory homogenizer at 7,500 to produce an oil in water emulsionhaving an average particle size of about 0.35 micrometers. The emulsionwas polymerized by adding 8 g of 4N hydrochloric acid to the emulsionand shaking it for several minutes in a closed container. The emulsionwas allowed to stand at room temperature for 20 hrs. without agitationto complete the polymerization process. Emulsion polymerization wasterminated by adding enough 2% aqueous sodium hydroxide solution toraise the pH of the emulsion to 6.5- 7.0. Emulsion A consisted of anapproximately 62 percent by weight solids emulsion of hydroxylendblocked polydimethylsiloxane (weight average molecular weight about220,000) and it contained 100 parts by weight platinum per one millionparts by weight polydimethylsiloxane. The emulsion was reserved forlater use.

Next, emulsion B was prepared by stirring together 648.9 g of thetrimethylsiloxy endblocked polymethylhydrogensiloxane of Example 1.26.5g of a 30 percent by weight aqueous sodium lauryl sulfate solution,and 309.8 g of deionized water for 30 minutes followed by homogenizingusing a laboratory homogenizer. Two passes were made through thehomogenizer to produce an emulsion having an average particle size ofabout 0.3 micrometers. Emulsion B consisted of an approximately 64%solids by weight aqueous emulsion of polymethylhydrogensiloxane.

Five aliquots of emulsion A were weighed into vials followed by enoughemulsion B to provide samples having 0.5, 1.0, 1.5, 2.0 and 5.0 per centpolymethylhydrogensiloxane fluid by weight of polydimethylsiloxaneemulsion polymer. The vials were capped and shaken for 30 minutesfollowed by lightly centrifuging them to exclude air bubbles from theemulsion. Next films were cast from these emulsions by pouring 10 g ofemulsion into Petri dishes and allowing them air dry for 24 hours. Allof the resulting films were elastomeric. However, the film prepared fromthe emulsion that contained 5.0 weight percentpolymethylhydrogensiloxane fluid was of very poor quality; it had verylow tensile strength and very low elongation. The sample containing 1.5per cent polymethylhydrogensiloxane fluid gave the film having the bestproperties.

EXAMPLE 4

This comparative example shows the effect of following the process ofmethod two, but not emulsifying the platinum catalyst.

To 645.6 g of the hydroxyl endblocked polydimethylsiloxane of Example 1was added 3.24 g of the polymethylhydrogensiloxane fluid of Example 1and the mixture was stirred several minutes until dissolution occurred.Then, 25 g of a 30 percent by weight aqueous solution of sodium laurylsulfate and 309.8g of deionized water were added and the mixture wasstirred for 30 minutes. Next the mixture was homogenized using alaboratory single stage homogenizer at 7500 psi to produce an emulsionhaving an average particle size of 0.33 micrometers and a solids contentof about 62-65 percent by weight. The emulsion was polymerized by adding6g of 4N hydrochloric acid and shaking the emulsion several minutes in aclosed container. The emulsion was allowed to stand at room temperaturefor 20 hrs, after which polymerization was terminated by adding enough2% aqueous sodium hydroxide solution to raise pH to 6.5-7.5. Thisemulsion consisted of a polydimethylsiloxane /5 percent by weightpolymethylhydrogensiloxane copolymer.

To 20 g of the above emulsion contained in a vial was added 0.19 g ofthe platinum catalyst of Example 1 and the vial was capped and shakenfor 24 hours. Next the vial was lightly centrifuged to exclude airbubbles from the emulsion, the emulsion was poured into a Petri dish andit was allowed to air dry for four days. The resulting film waselastomeric, but contained dark spots believed to be caused by poordispersion of the platinum compound catalyst.

EXAMPLE 5

An emulsion was prepared following method two in which the amount ofpolydimethylsiloxane in emulsion B was 0.

First an emulsion A was prepared by mixing 645.6 g of the hydroxylendblocked polydimethylsiloxane fluid of example 1 and 3.24 g of thepolymethylhydrogen siloxane fluid of example 1 and stirring severalminutes until dissolution occurred. Then 25 g of a 30 percent aqueoussolution of sodium lauryl sulfate and 309.8 g of deionized water wereadded and the mixture was stirred for 30 minutes. Next the mixture washomogenized using a laboratory single stage homogenizer at 7500 psi toproduce an emulsion having an average particle size of 0.33 micrometersand a solids content of about 62-65 percent by weight. The emulsion waspolymerized by adding 6g of 4N hydrochloric acid and shaking theemulsion several minutes in a closed container. The emulsion was allowedto stand at room temperature for 20 hrs after which polymerization wasterminated by adding enough 2 percent aqueous sodium hydroxide solutionto raise pH to 6.5-7.5. This emulsion consisted of apolydimethylsiloxane / 5 weight percent polymethylhydrogensiloxanecopolymer.

Then emulsion B was prepared by mixing 300 g of the chloroplatinic acidcomplex of example 1.15 g of a 30 per cent aqueous solution of sodiumlauryl sulfate and 285 g of deionized water for 30 minutes followed byhomogenizing using a single stage laboratory homogenizer. Three passesat 7500 psi were required to produce an emulsion of uniform particlesize. Emulsion B consisted of a 50 per cent by weight solids emulsion ofplatinum catalyst. The platinum concentration in emulsion B wasapproximately 0.33 per cent by weight.

Then 20 g of emulsion A was weighed into a vial followed by 0.38 g ofemulsion B. The vial was capped, shaken for 30 minutes and lightlycentrifuged to exclude air bubbles. The emulsion was poured into a Petridish and allowed to air dry at ambient conditions for 24 hrs. Theresulting film was elastomeric. There were no dark spots in this sample,indicating that the platinum was well dispersed when compared to theresult of comparative example 4.

EXAMPLE 6

A comparative example was prepared using the same ingredients as inExample 1, but in which each ingredient, (1), (2), and (3) were inseparate emulsions.

An Emulsion A was prepared by mixing 648.9 g of the hydroxyl endblockedpolydimethylsiloxane fluid of Example 1, 26.5 g of a 30 percent aqueoussolution of sodium lauryl sulfate and 309.8 g of deionized water into abeaker and stirring the mixture for 30 minutes. The mixture was thenhomogenized using a single stage laboratory homogenizer at 7.500 psi toproduce an oil in water emulsion having an average particle size ofabout 0.35 micrometer. The emulsion was polymerized by adding 8 g of 4Nhydrochloric acid to the emulsion and shaking it for several minutes ina closed container. The emulsion was allowed to stand at roomtemperature for 20 hrs. without agitation to complete the polymerizationprocess. Emulsion polymerization was terminated by adding enough 2percent aqueous sodium hydroxide solution to raise the pH of theemulsion to 6.5-7.0.

Emulsion A consisted of an approximately 62% by weight solids emulsionof hydroxyl endblocked polydimethylsiloxane (weight average molecularweight about 220,000).

An Emulsion B was prepared by mixing 648.9 g of thepolymethylhydrogensiloxane of Example 1. 26.5g of a 30 percent by weightaqueous sodium lauryl sulfate solution and 309.8 g of deionized waterwere stirred for 30 minutes followed by homogenizing using a laboratoryhomogenizer. Two passes were made through the homogenizer to produce anemulsion having an average particle size of about 0.3 micrometer.Emulsion B consisted of an approximately 64 percent solids by weightaqueous emulsion of polymethylhydrogensiloxane.

Then an Emulsion C was prepared by mixing 300 g of the chloroplatinicacid complex of Example 1, 15 g of a 30 per cent aqueous solution ofsodium lauryl sulfate and 285 g of deionized water for 30 minutesfollowed by homogenizing using a single stage laboratory homogenizer.Three passes at 7500 psi were required to produce an emulsion of uniformparticle size. Emulsion C consisted of a 50 per cent by weight solidsemulsion of the platinum complex catalyst. Platinum concentration inemulsion C was approximately 0.33 per cent by weight.

Three 20 g aliquots of emulsion A were weighed into vials followed byenough emulsion B to provide samples having 0.5, 2.0 and 5.0 per centpolymethylhydrogensiloxane fluid by weight of polydimethylsiloxaneemulsion polymer. Next 0.38 g of emulsion C was added to each vial, andthey were capped and shaken for 30 minutes followed by lightlycentrifuging them to exclude air bubbles from the emulsions. Next filmswere cast from these emulsions by pouring lOg of emulsion into Petridishes and allowing them to air dry for 24 hours. None of the resultingfilms cured to form an elastomer. Instead, each film consisted of tackygum. Another 20 g aliquot of emulsion A was mixed with enough emulsion Bto make a sample having 10 per cent polymethylhydrogensiloxane fluid byweight of polydimethylsiloxane. Then 0.38 g of emulsion C was added, theemulsion was shaken for 30 minutes, centrifuged and poured into a Petridish. After 24 hours, the resulting composition had cured, but it wasnot elastomeric. Although it was not tacky, it was extremely weak andfriable, but not elastomeric.

EXAMPLE 7

An Emulsion A was produced by mixing 648.9 g of the hydroxyl endblockedpolydimethylsiloxane fluid of Example 1, and 10.7 g of thechloroplatinic acid complex of Example 1 for several minutes to effectdissolution. Next 26.5g of a 30% aqueous solution of sodium laurylsulfate and 309.8 g of deionized water were added and the mixture wasstirred for 30 minutes. The mixture was homogenized using a single stagelaboratory homogenizer at 7,500 to produce an oil in water emulsionhaving an average particle size of about 0.35 micrometers. The emulsionwas polymerized by adding 8g of 4N hydrochloric acid to the emulsion andshaking it for several minutes in a closed container. The emulsion wasallowed to stand at room temperature for 20 hrs. without agitation tocomplete the polymerization process. Emulsion polymerization wasterminated by adding enough 2 percent aqueous sodium hydroxide solutionto raise pH of the emulsion to 6.5-7.0. Emulsion A consisted of anapproximately 62% by weight solids emulsion of hydroxyl endblockedpolydimethylsiloxane (weight average molecular weight about 220,000) andit contained 100 parts per million by weight of platinum. The emulsionwas reserved for later use.

An emulsion was prepared by mixing 50 parts by weight of the reactionproduct obtained from reacting an acidic mixture of 50 parts by weightof solid, benzene soluble resin copolymer consisting essentially ofMe3SiO1/2 units and SiO4/2 units at a ratio of about 0.75to 1.0 as asolvent solution, and 50 parts by weight of trimethylsiloxy endblockedpolymethylhydrogensiloxane having a viscosity of about 0.13 Pa.s at 25°C. and a silicon-bonded hydrogen atom content of about 1.6 percent byweight, and removing the solvent, the reaction product being about 97percent non-volatile content with a viscosity at 25° C. of about 1.3Pa.s, a hydroxy content of about 1.6 percent by weight, and a hydrogencontent of about 0.8 percent by weight with 29.5 parts of an aqueousphase consisting of 27 parts of water, 0.5 parts of sodiumalkylarylpolyether sulfonate (Triton X-200, Rhom and Haas Co.. Inc.Philadelphia. Pa.), 1.33 parts of polyvinylalcohol (PVA) havingapproximately 12 percent unhydrolyzed vinyl acetate groups and aviscosity, at 4 percent solids in water, of 22 mPa.s and 0.67 parts ofPVA having approximately 12 percent unhydrolyzed vinyl acetate groupsand a viscosity, at 4 percent solids in water, of 5 mPa.s; passing themixture through a colloid mill and stirring the resulting emulsion into20.5 parts of water. The final emulsion had a calculated solids contentof 52 percent and a calculated liquid silicone resin/PVA ratio of 25,based upon the amounts used. This was emulsion B.

Four 20 g aliquots of emulsion A were weighed into vials followed byenough emulsion B to provide samples having 1.0, 2.0, 3.0 and 5.0 percent by weight of the reaction product in emulsion B. The vials wereshaken for 30 minutes and centrifuged lightly to remove air bubbles fromthe emulsions. Films were cast by pouring approximately 10 g of eachemulsion into a Petri dish and allowing it to dry under ambientconditions for 24 hours. Each of the resulting films was elastomeric.

EXAMPLE 8

A comparative example was prepared using the same ingredients as inEXAMPLE 7 with the ingredients in separate emulsions.

An emulsion A was prepared as in EXAMPLE 6, giving an emulsion ofhydroxyl endblocked polydimethylsiloxane fluid.

An emulsion B was prepared as in EXAMPLE 7, givng an emulsion of siliconhydride crosslinker.

An emulsion C was prepared as in EXAMPLE 6, giving an emulsion ofplatinum compound catalyst.

Three 20 g aliquots of emulsion A were weighed into vials followed byenough emulsion B to provide samples having 1.0, 2.0 and 5.0 per cent ofthe reaction product in emulsion B based on the weight ofpolydimethylsiloxane. Next 0.38 g of emulsion C was added to each vial,and the vials were shaken for 30 minutes followed by lightlycentrifuging them to exclude air bubbles from the emulsions. Next filmswere cast by pouring 10 g of emulsion into Petri dishes and allowingthem to air dry for 24 hours. None of the resulting films cured to forman elastomer. As in EXAMPLE 6, each film was a tacky, sticky gum.

That which is claimed is:
 1. A method of producing an aqueous siliconeemulsion which dries to an elastomer comprising(A) homogenizing amixture of(1) 100 parts by weight of hydroxyl endblockedpolydiorganosiloxane free of aliphatic unsaturation, (2) from 0.1 to 10parts by weight of silicon hydride crosslinker, (3) sufficient platinumcompound catalyst, compatible with the polydiorganosiloxane, to givefrom 1 to 200 parts by weight of platinum per million parts ofpolydiorganosiloxane (1), (4) catalyst inhibitor, (5) anionic ornonionic surfactant, and (6) sufficient water to yield apolydiorganosiloxane content in the mixture of from 40 to 70 percent byweight, the catalyst inhibitor (4) being added to the mixture before thecatalyst (3), (B) emulsion polymerizing the mixture of (A) by additionof anionic polymerization catalyst to give a polymer, then, (C)arresting polymerization by raising the pH to 6 to 7.5, whereby anaqueous silicone emulsion is obtained which gives an elastomer uponremoval of the water at room temperature.
 2. The method of claim 1 inwhich (1) has a viscosity of less than 250 centipoise at 25° C.
 3. Themethod of claim 2 in which (2) is from 0.5 to 2 parts by weight of theweight of (1) and is a trimethylsilyl endblockedpolymethylhydrogensiloxane.
 4. The method of claim 3 in which (3) is thereaction product of chloroplatinic acid and an organosilicon compoundcontaining terminal aliphatic unsaturation.
 5. The method of claim 4 inwhich (4) is diethylmaleate.
 6. The method of claim 4 which adds step(D) admixing filler.
 7. The aqueous silicone emulsion produced by themethod comprising(A) homogenizing a mixture of(1) 100 parts by weight ofhydroxyl endblocked polydiorganosiloxane free of aliphatic unsaturationand having a viscosity of less than 250 centipoise at 25° C., (2) from0.1 to 10 parts by weight of silicon hydride crosslinker, (3) sufficientplatinum compound catalyst, compatible with the polydiorganosiloxane, togive from 1 to 200 parts by weight of platinum per million parts ofpolydiorganosiloxane (1), (4) catalyst inhibitor, (5) anionic ornonionic surfactant, and (6) sufficient water to yield apolydiorganosiloxane content in the mixture of from 40 to 70 percent byweight, (B) emulsion polymerizing the mixture of (A) by addition ofanionic polymerization catalyst to give a polymer, then, (C) arrestingpolymerization by raising the pH to 6 to 7.5, whereby an aqueoussilicone emulsion is obtained which gives an elastomer upon removal ofthe water at room temperature.
 8. The aqueous silicone emulsion producedby the method comprising(A) homogenizing a mixture of(1) 100 parts byweight of hydroxyl endblocked polydiorganosiloxane free of aliphaticunsaturation and having a viscosity of less than 250 centipoise at 25°C., (2) from 0.5 to 2 parts by weight of trimethylsilyl endblockedpolymethylhydrogensiloxane, (3) sufficient reaction product ofchloroplatinic acid and an organosilicon compound containing terminalaliphatic unsaturation, to give from 1 to 200 parts by weight ofplatinum per million parts of polydiorganosiloxane (1), (4) catalystinhibitor, (5) anionic or nonionic surfactant, and (6) sufficient waterto yield a polydiorganosiloxane content in the mixture of from 40 to 70percent by weight, (B) emulsion polymerizing the mixture of (A) byaddition of anionic polymerization catalyst to give a polymer, then, (C)arresting polymerization by raising the pH to 6 to 7.5, and (D) admixingfiller, whereby an aqueous silicone emulsion is obtained which gives anelastomer upon removal of the water at room temperature.